The present invention relates to a method for stereoscopic analysis of the textural structure of a food of a multi-component dispersion system, the food containing at least one component (i.e., member; the same applies hereafter) selected from among starches, proteins, and lipids.
Starches, proteins, and lipids are accepted to be three major nutrient groups of foods. Wheat flour or rice is a principal raw material of a certain class of processed foods including breads, noodles, cooked rice, confectioneries, and tenpura, and taste and oral sensation imparted by a food are considered to be greatly affected by the form of the three major nutrients contained in the food. Conventionally, taste and oral sensation of the above foods have been evaluated through sensory testing. In recent years, attempts have been made to elucidate the textural structure of food through use of apparatus and devices, and on the basis of the thus-clarified textural structure, to determine oral sensation, etc. However, observation of the textural structure through use of such apparatus and devices does not necessarily lead to satisfactory evaluation, in that borders between respective components are sometimes unclear, or captured images are planar and non-stereoscopic.
For example, in the case of observation through an electron microscope, an electron beam is applied to a specimen and reflected electrons are detected for observation of shapes of the specimen (scanning electron microscopy), or, alternatively, differences between the information provided by electrons that have penetrated the sample and the information provided by electrons that have not penetrated the sample are detected for observation of shapes of the specimen (transmission electron microscopy). These methods enable observation of a specimen at very high resolution, but since these methods do not permit staining of samples, discrimination of specific components is difficult, thereby preventing structural analysis of borders between the components.
In the case of observation through an optical microscope, specific components of a specimen are stained before observation of the specimen. In this case also, border portions are unclear. When multi-staining is performed, some extent of segmentation by color is possible, but staining specificity is small and dyes overlap, substantially preventing discernment of the textural structure.
A confocal laser microscope can concentrate intense light that travels along a highly straight path to a single point through use of laser light. Using such laser light, the confocal laser microscope can provide correctly focused images and sectional images of deep focal depths, whereby images of high contrast can be obtained. However, confocal laser microscopy does not permit staining of specimens, and thus discrimination of specific components is difficult, whereby structural analysis of borders between the components becomes difficult.
The present inventors have performed extensive studies regarding image analysis methodology that enables clear, definite discernment with respect to the complex textural structure of food of a multi-component dispersion system, the food containing starches, proteins, and lipids, thereby leading to completion of the invention.
Accordingly, the present invention is directed to a method for analysis of the textural structure of a food of a multi-component dispersion system, characterized by comprising staining food containing at least one component selected from among starches, proteins, and lipids with at least one species of a fluorescent dye, and observing the stained food within a wavelength range lower than the value calculated by subtracting 40 nm from the maximum absorption wavelength of the employed fluorescent dye, preferably within a wavelength range lower than the value calculated by subtracting 50 nm from the maximum absorption wavelength of the employed fluorescent dye, more preferably within a wavelength range lower than the value calculated by subtracting 70 nm from the maximum absorption wavelength of the employed fluorescent dye.
The present invention is also directed to a method for analysis of the textural structure of a food of a multi-component dispersion system, characterized by comprising staining food containing at least one component selected from among starches, proteins, and lipids with at least one species of a fluorescent dye, observing the stained food at two or more different wavelengths which fall within a wavelength range lower than the value calculated by subtracting 40 nm from the maximum absorption wavelength of the employed fluorescent dye, and synthesizing at least two obtained images (hereinafter referred to as an image synthesis method).